Velocity control system for air conveyors

ABSTRACT

The system includes a deck having multiple openings for communicating air from an underlying plenum to lift and advance an object along a predetermined path spaced above and adjacent the deck. To retard fast moving objects without affecting slower moving objects, a barrier is disposed in the path of movement of the objects. Enlarged openings are provided through the deck directly upstream of the barrier to provide a lifting airjet of increased capacity. The fast moving objects have sufficient forward momentum to penetrate the larger capacity lifting airjet and strike the barrier. The larger capacity airjet lifts the stopped object over the barrier whereupon the object again starts moving downstream. The slower moving objects are lifted by the larger capacity airjet to an elevation above the barrier prior to hitting the barrier and are thus conveyed over the barrier without significant loss of velocity.

United States Patent Hurd et al.

[ 1 Mar. 7, 1972 [54] VELOCITY CONTROL SYSTEM FOR AIR CONVEYORS [72]Inventors: Stanley E. Hurd, Sunnyvale; Leong Q.

Fong, San Jose, both of Calif.

Bangor Pimta Operations, lnc., Greenwich, Conn.

Jan. 8, 1971 [73] Assignee:

[22] Filed:

. 211 App1.No.: 104,869

Primary Examiner-Evon C. Blunk Assistant Examiner-Hadd S. LaneAttorney-Patrick J. Walsh ABSTRACT The system includes a deck havingmultiple openings for com municating air from an underlying plenum tolift and advance an object along a predetermined path spaced above andad jacent the deck. To retard fast moving objects without affectingslower moving objects, a barrier is disposed in the path of movement ofthe objects. Enlarged openings are provided through the deck directlyupstream of the barrier to provide a lifting airjet of increasedcapacity; The fast moving objects have sufficient forward momentum topenetrate the larger capacity lifting airjet and strike the barrier. Thelarger capacity airjet lifts the stopped object over the barrierwhereupon the object again starts moving downstream. The slower movingobjects are lifted by the larger capacity airjet to an elevation abovethe barrier prior to hitting the barrier and are thus conveyed over thebarrier without significant loss of velocity.

14 Claims, 1 1 Drawing Figures PAIENTEUM m2 SHEET10F4 PATENTEDMAR 719123,647,266

SHEET 2 [IF 4 INVENTORS i E. im/46y E Hueo BY 160M? Q fE/YG IPATENTEDMAR H972 3,647.266

SHEET 3 OF 4 I N VEN TORS 5779 746) f/ueo VELOCITY CONTROL SYSTEM FORAIR CONVEYORS The present invention relates to a velocity control systemfor air conveyed objects and particularly relates to a velocity controlsystem which discriminates between fast and slow moving objects andretards or stops the faster moving objects without significantlyretarding or stopping the slower moving objects.

Air conveyors for moving objects along a predetermined path withoutphysical contact between the objects and the conveyor are known in theprior art. One of the difficulties in air conveying systems is that theobjects, when in motion, continue to accelerate and obtain such excessvelocity as to preclude control over the objects. Moreover, the excessvelocity subjects the objects to damaging impact whenever they arestopped at the end of or on the conveyor. It is therefore desirable toreduce the speed of the faster moving air conveyed objects to or below apredetermined'velocity.

It will be appreciated that, in air conveyor systems, there are a largenumber of variables including the weight and dimensional characteristicsof the objects being conveyed which determine the required and/ordesirable lifting and propelling forces which, in turn, determine thespeed at which the objects are conveyed. Consequently, specified objectsconveyed along an air conveyor obtain various velocities. While it maytherefore be desirable to retard or periodically stop objects beingconveyed at velocities in excess of a predetermined velocity in order toretain control over objects, it is also desirable that the velocitycontrol device not significantly affect the velocity of objects beingmoved along the air conveyor at slower velocity, i.e., at or below thepredetermined velocity, in order that accumulation recovery rates forthe conveyor are not significantly affected. Thus, a significantconsideration in the design of an effective velocity control system foran air conveyor is the desirability to discriminate between fast andslow moving objects whereby accumulation recovery rates are notadversely affected.

The present invention uniquely fulfills the foregoing describedrequirements for an air conveyor and provides a velocity control deviceat one or more predetermined locatioiis along the conveyor. The velocitycontrol device includes a barrier or stop in the path of movement ofobjects conveyed which, in conjunction with the disposition of one ormore enlarged openings in the conveyor deck immediately upstream of thelocation of the stop, operates to retard or stop fast moving objectswithout significantly affecting the rate of movement of slower movingobjects. In one embodiment of the present invention, a stop bar isdisposed on the conveyor deck in the path of movement of the objects.The desk is disposed over a plenum and has lifting holes and directionalslots through which lifting and directional airjets issue and which jetscooperate to convey objects downstream along a cushion of air. Anenlarged opening is provided in the deck immediately adjacent the stopbar on the upstream side thereof whereby a lifting jet of enlargedcapacity is provided. In operation, a fast moving object being conveyedalong the conveyor deck has sufficient forward mementum to fullypenetrate the larger lifting airjet issuing through the enlarged openingbefore the jet is effective to elevate the object over the bar. The fastmoving object thus strikes the bar and its forward motion is momentarilystopped. This larger lifting jet then becomes effective to lift theobject to a height such that it clears the bar. The object then startsto move forwardly and begins to accelerate in the downstream direction.The velocity of the fast moving object is thus slowed considerably inthe area immediately beyond the stop and control over the object is thusretained. When a slower moving object reaches the area of the stop bar,its forward momentum is insufiicient to carry it completely through orto fully penetrate the larger airjet prior to the latter air jetbecoming fully effective to lift the object over the stop bar.Accordingly, the slower moving object does not strike the stop bar andits rate of movement along the conveyor is thus not significantlyaffected as it passes over the barrier and enlarged capacity liftingjet. The velocity control device hereof thus discriminates between fastand slow moving objects, slowing down the fast moving objects while notsignificantly affecting the rate of movement of the slower movingobjects.

In another form hereof, a barrier in the form of a rod is disposedacross the conveyor deck in the path of movement of the objects,opposite ends of the rod being carried in inclined slots. The rod isspring biased and provides a resilient stop against which the fastmoving objects engage. Enlarged openings are provided in the deck onopposite sides of the rod and the larger airjets issuing therefrom liftthe objects over the rod for further forward movement along theconveyor. In a still further form hereof, a stop plate is pivotallymounted on the conveyor deck. When the plate is pivoted upwardly, itsupstream edge forms a stop against which the objects may engage. Theforward edge of the plate and the downstream edge of the deck adjacentthe forward edge of the plate provide an enlarged opening. The undersurface of the plate adjacent its upstream edge is inclined to direct anairjet issuing through the enlarged opening upwardly and in a slightlyupstream direction. The enlarged airjet is directed diagonally throughthe slot to provide optimum lift to the object and thereby lift it overthe plate. In a still further form hereof, a bar is disposed across theconveyor deck in the path of movement of the object. Opposite ends ofthe bar are located in guides along the opposite sides of the conveyordeck and the rod is freely mounted in the guides for vertical movement.An enlarged lift hole is disposed below the rod and the lifting jetissuing therethrough maintains the rod in an uppermost floating positionbearing against the lower ends of screws threaded into the guides. Theheight of the rod above the conveyor deck can be adjusted by threadingthe screws. Again, fast moving objects are stopped by the rod and thenlifted over the rod by the large airjet. The slower moving objects passover the rod without significant affect on their rate of movement alongthe conveyor.

Accordingly, it is a primary object of the present invention to providea novel and improved velocity control system for air conveyed objects.

It is another object of the present invention to provide a velocitycontrol system for air conveyed objects which discriminates between fastand slow-moving objects whereby fast-moving objects are slowed while thevelocity of slower moving objects is not substantially affected.

It is still another object of the present invention to provide avelocity control system for air conveyed objects which does not requiremoving parts, control sensors or other mechanisms of a similar type.

It is a further object of the present invention to provide a velocitycontrol system for air conveyed objects which does not substantiallyaffect the accumulation recovery rates of the conveyor.

It is still a further object of the present invention to provide avelocity control system for air conveyed objects which is simple andinexpensive to construct and does not require protrusions or othermechanisms above the conveyor area.

These and further objects and advantages of the present invention willbecome more apparent upon reference to the following specification,appended claims and drawings wherein;

FIG. 1 is a perspective view of an air conveyor incorporat ing avelocity control system constructed in accordance with the presentinvention;

FIG. 2 is a fragmentary vertical cross-sectional view thereofillustrating the manner in which a fast moving object is slowed;

FIG. 3 is a cross-sectional view taken generally about on lines 33 inFIG. 2;

FIG. 4 is a fragmentary perspective view of a directional slot employedin the air conveyor illustrated in FIG. 1;

FIG. 5 is a fragmentary perspective view of an air conveyor employinganother form of velocity control system therefor;

FIG. 6 is an enlarged fragmentary cross-sectional view of the stoppingdevice employed in the velocity control system illustrated in FIG. 5;

FIG. 7 is a fragmentary cross-sectional view taken generally about onlines 7-7 in FIG. 5',

FIG. 8 is a fragmentary perspective view of an air conveyor employingstill another form of velocity control system therefor;

FIG. 9 is a fragmentary vertical cross-sectional view of the stopmechanism employed with the velocity control system illustrated in FIG.8;

FIG. 10 is a fragmentary perspective view of an air conveyor employing astill further form of velocity control system therefor; and

FIG. 11 is an enlarged cross-sectional view of the stopping mechanismemployed with the velocity control system illustrated in FIG. 10.

Referring now to the drawings, particularly to FIGS. 1 -4, there isillustrated an air conveyor, generally indicated 10, having elongatedside and bottom walls 12 and I4 respectively, and an elongated conveyordeck 16, the walls and deck enclosing an elongated plenum 18. An airblower is provided at one end of conveyor 10 for supplying air to plenum18. The air in plenum 18 is adapted to communicate upwardly through aplurality of openings in conveyor deck 16. Particularly, the openingscomprise lift holes 22 and directional slots 24. The lift holes 22 areconfigured to issue air from plenum 18 in the form of a substantiallyvertically directed jet for the purpose of lifting an object, forexample the box 26 illustrated in FIG. 1, above deck l6. Slots 24 areconfigured to issue air from plenum 18 in the form of a jet having apredominantly horizontal flow component above deck 16 for the purpose ofpropelling an object along conveyor 10. The lift holes and directionalslots may be arranged in conveyor deck 16 in any suitable manner, forexample as illustrated in U.S. Pat. No. 3,l80,688 or in copendingapplication, Ser. No. 106,056 filed Jan. I3, I971, of common assigneeherewith. It is sufficient for present purposes to note that the liftholes 22 and directional slots 24 respectively function to maintain theobjects in spaced relation above conveyor deck 16 and to propel themalong conveyor 10 in the desired direction respectively. A pair of guiderails 28 are also provided along opposite sides of deck 16.

As noted hereinbefore, the air issuing through directional slots 24tends to continue to accelerate objects 26 along conveyor 10. That is tosay, when an object 26 is set in motion, its velocity increases and thisresults in decreasing capability to control the object. Consequently,after object 26 has moved a predetermined distance along conveyor 10, itis desirable to stop or retard the object.

In order to accomplish this, and before object 26 obtains a velocitybeyond which control over the object becomes virtually impossible, thereis provided along conveyor 10 a velocity control station generallyindicated at 30. Control station 30 includes, in the form hereofillustrated in FIGS. 1 4, an elongated bar 32 disposed across conveyordeck 16 in the path of movement of the objects being conveyed alongconveyor 10. That is to say, bar 32 projects upwardly above the surfaceof deck 16 sufficiently to intercept an object conveyed along conveyor10 and provides a barrier against which an object may be stopped(depending on the rate of movement of the object at that position alongthe conveyor as explained hereinafter). Control station 30 also includesan enlarged opening 34 through deck 16 in communication with plenum 18.Opening 34 is located immediately adjacent bar 32 on the upstream sidethereof. It will be appreciated that the air jet issuing through opening34 from plenum I8 and which jet is directed against the undersurface ofan object being conveyed when the latter obtains a position adjacent bar32, provides an increased lifting force sufficient to elevate the objectabove bar 32 whereby the object can be passed over bar 32 as moreparticularly described hereinafter. The velocity control device hereofis located along conveyor 10 at one or more stations in accordance withthe distances traversed by the objects and the velocities therebyobtained.

In use, it will be appreciated that a fast-moving object conveyed alongconveyor 10 by air issuing through directional slots 26 has sufficientforward momentum to penetrate completely and pass through the liftingairjet issuing through enlarged opening 34 before the airjet is fullyeffective to lift the object over bar 32. Bar 32 thus momentarily stopsobject 28 from further forward movement until the lifting jet becomeseffective to elevate the object to a height above bar 32. When object 28or at least its leading edge obtains this height, directional slots 26in deck 16 propel object 28 in a forward direction along conveyor 10.However, since the object was at least momentarily stopped by bar 32, itwill start to accelerate along conveyor 10 at a reduced velocity. Thevelocity of the object will increase as it is conveyed away fromvelocity control station 30 to either an off-loading station or toanother velocity control station whereupon the velocity of thefast-moving object would again be reduced.

For slower moving objects, the airjet issuing through enlarged opening34 creates sufficient lifting force such that the slow moving objects donot fully penetrate or pass completely through the lifting jet before itbecomes effective to elevate such objects to a height greater than theheight of bar 32. At such elevation, the slower moving objects pass overbar 32 without physical contact therewith. Thus the velocity of theslower moving object along conveyor 10 is not significantly affected bythe interposition of the velocity control device. Also, the velocitycontrol device discriminates between fast and slow-moving objects andretards the movement of the former without significantly affectingmovement of the latter. In this manner, the accumulation rates of theconveyor are also not substantially affected by the interposition of thevelocity control device.

Referring now to the embodiment hereof illustrated in FIGS. 5 7, thereis disclosed an air conveyor 10a similar to air conveyor 10 with theexception that the instant embodiment includes a modified velocitycontrol device. In this form, there is provided a pair of brackets 40adjustably mounted along opposite sides of the conveyor deck 16a atvelocity control station 30a. Each of brackets 40 includes a slot 42angled upwardly and in a downstream direction and in which slot 42 isreceived the opposite ends of a bar 44. Opposite ends of bar 44 areconnected to ends of coil springs 46, the opposite ends of coil springs46 being fixed to brackets 48 secured to conveyor deck 16a. Brackets 40and 48 are adjustably secured to conveyor deck 16a for longitudinalmovement for purposes as will be described. It will be appreciated thatsprings 46 maintain bar 44 in the upstream ends of slots 42 and in aposition elevated above deck 16a in the path of movement of objectsalong conveyor 10a.

The openings through conveyor deck 16a for the purpose of lifting andpropelling objects along conveyor 10a are identical to the openings inconveyor 10 described previously with respect to FIGS. 1 4. In thisform, however, there are pro-v vided a plurality of lift holes 50 spacedone from the other in a pair of rows extending transversely across deck16a and straddling bar 44. That is to say, the airjets issuing throughopenings 50 from plenum 18a are directed upwardly on opposite sides ofbar 44 when the latter lies in its retracted upstream position. As willbe appreciated, openings 50 are of enlarged diameter as compared withlift holes 22a with the result that an object superposed over openings50 is subjected to increased lifting forces in comparison with thenormal lifting forces of the jets issuing through holes 22a.

In utilizing the velocity control system illustrated in FIGS. 5 7, anobject 280 is conveyed along conveyor 10a similarly as previouslydescribed. If the object is a relatively fast-moving object, it hassufficient forward momentum to penetrate and pass completely through thelifting jets issuing through the upstream row of openings 50 before suchairjets are fully effective to lift the object 28a over bar 44. Theobject 28a thus engages bar 44 and its forward movement is momentarilyarrested. The forward momentum of the relatively fast moving object 28amay also be sufficient to displace the bar 44 in a downstream directionagainst the bias of springs 46. Displacement of bar 44 in a downstreamdirection permits the air jets issuing through the openings 50 on thedownstream side of bar 44 to become effective against object 280. Theairjets issuing through both rows of enlarged openings 50 then becomeeffective to elevate the object above bar 44 whereupon the air issuingfrom directional slots 24a acts to accelerate the object in a downstreamdirection at a reduced velocity. Again, it will be appreciated that theforward motion of the object is substantially arrested by its engagementwith bar 44 and that, when the object is elevated to clear bar 44, itmoves downstream at a relatively slower velocity than obtained uponfirst encountering the flow control station. Furthermore, by utilizing aspring biased bar, a cushioned or resilient stop is obtained. Moreover,since bar 44 is located at a higher position when the lifting jetsissuing through the downstream row of transverse openings 50 becomeeffective, greater control over the object as it clears bar 44 isobtained. Further, the location of velocity control device 30a can beadjusted to a limited extent longitudinally along conveyor l0a dependingupon the nature of the objects being conveyed and the desired lift forceat the control station.

For slower moving objects, the airjets issuing through openings 50create sufficient lifting force such that the slowmoving objects do notfully penetrate or pass completely through the airjet before they becomeeffective to elevate such objects to a height greater than the height ofbar 44. At such elevation, the slower moving objects pass over bar 44without physical contact therewith. Thus the velocity of a slower movingobject along conveyor a is not significantly affected by theinterposition of the velocity control device. Also, velocity controldevice 30a discriminates between fast and slow-moving objects andretards the movement of the former without significantly affectingmovement of the latter.

Referring now to the embodiment hereof illustrated in FIGS. 8 9, thereis disclosed an air conveyor 10b similar to the air conveyor 10illustrated in FIGS. 1 4 having like lifting openings and directionalslots for conveying an object along conveyor deck 16b. In this form, thevelocity control device includes a plate 60 which forms a portion of airconveyor deck 16b and has directional slots 62 and lift openings 64interspersed therein similarly as deck 16b. Plate 60 is pivoted at itsdownstream edge to deck 16b and carries an angled stop plate 66 over itsupstream edge. Stop plate 66 extends laterally substantiallycoextensively with plate 60. The lower leg 68 of stop plate 66 isinclined downwardly and in a downstream direction and serves as a bafflefor directing an airjet diagonally upwardly and in an upstream directionthrough a slot 67 defined between leg 68 and the downstream edge of deck16b adjacent plate 60. Optimum lift characteristics are obtained bydirecting the airjet in this manner. A pair of brackets 69 are carriedalong the inside upper edges of sidewalls 12b of conveyor 10b. Asetscrew 70 and a locking screw 72 are provided through plate 60 alongits opposite sides adjacent its leading edge, the locking screw beingthreadedly engageable with plate 69 and the set screw bearingthereagainst whereby the elevation of plate 60 relative to conveyor deck16b can be adjusted. A pair of angle brackets 74 are provided onopposite sides of plate 60 and serve to confine the airflow from plenum18b for issuance through slot 67.

In use, plate 60 is pivoted about its downstream edge such that stopplate 66 obtains the desired elevation above deck 16b and the setscrewsand locking screws are then adjusted to retain the plate in the desiredelevation. This elevation also determines the size of slot 67. As in theprevious embodiments, when a fast moving object approaches the elevatedplate 60, its forward momentum is sufficient to carry it through thelarger lifting jet issuing through slot 67. The object is accordinglymomentarily stopped against stop plate 66. The lifting force provided bythe large airjet issuing through slot 67 then elevates the object to aheight above the upstream edge of stop plate 66. The directional slots62 in plate 60, in conjunction with the directional slots 24b in deck16b immediately upstream of plate 60, serve to propel the objectdownstream during its passage over plate 60 while the lifting openings64 in plate 60 maintain the object in spaced relation from plate 60similarly as it is maintained in spaced relation above deck 16b.

For slower moving objects, the airjet issuing through slot 67 createssufficient lifting force such that the slow moving objects do not fullypenetrate or pass completely through the airjet before it becomeseffective to elevate such objects to a height greater than the height ofstop plate 66. At such elevation, the slower moving objects passoverplate 60 without physical contact therewith. Thus the velocity of aslower moving object along conveyor 10b is not significantly affected bythe interposition of the velocity control device 30b. Also, velocitycontrol device 30b discriminates between fast and slow-moving objectsand retards the movement of the former without significantly affectingmovement of the latter.

Referring to the embodiment hereof illustrated in FIGS. 10 and 1 1,there is provided an air conveyor 100 similar to the air conveyor 10illustrated in FIGS. 1 4. In this form, velocity control device 30cincludes a pair of upstanding guides disposed on opposite sides of theconveyor 10c. The upstanding guides 80 provide slots 82 in which theopposite ends of a stop bar 84 are inserted, the bar 84 being mountedfor vertical movement within guides 80. A screw 86 is threaded throughthe top of each of the guides 80 for the purpose of controlling theheight of the rod 84 in a manner to be described. The velocity controldevice also includes a baffle 88 secured to the underside of deck 160 onthe downstream side of an enlarged slot 90 which extends across conveyordeck 16c directly below rod 84. The leg of baffle 88 is inclineddownwardly in a downstream direction and directs the airjet issuing fromplenum 18c and through slot 90 in a diagonally upward upstream directionwhich, as noted previously, provides for optimum liftingcharacteristics. In this form, the force of the airjet issuing throughslot 90 acts against bar 84 to lift and maintain the bar 84 in bearingengagement against the lower ends of the adjustment screws 86. That isto say, rod 84 floats within guide 80 and the elevation of rod 84 abovedeck 160 is controlled by threaded adjustment of screws 86.

In use, when a fast moving object reaches the velocity control station300, its forward momentum is sufficient to carry it through the largeairjet for engagement against stop bar 84 before the large airjetbecomes effective to lift the object over bar 84. Bar 84 thusmomentarily arrests the forward movement of the object until the liftingjet becomes effective to elevate the object above the bar 84 whereuponthe directional slots in conveyor deck 16c again serve to accelerate theobject along the conveyor but at a reduced velocity.

For slower moving objects, the airjet issuing through slot 90 createssufficient lifting force such that the slow moving objects do not fullypenetrate or pass completely through the airjet before it becomeseffective to elevate such objects to a height greater than the height ofrod 84. At such elevation, the slower moving objects passover rod 84without physical contact therewith. Thus the velocity of a slower movingobject along conveyor is not significantly affected by the interpositionof velocity control device 30c.

It will be appreciated that the objects of the present invention arefully accomplished by the foregoing in that there is provided in eachinstance a velocity control device which discriminates between fast andslow moving objects moved along the conveyor. In each case, thefast-moving objects have sufficient momentum to penetrate and passthrough the large lifting jet located at each velocity control stationbefore the lifting jet becomes fully effective to elevate the objects toa height sufficient to clear the barrier. Thus, the barrier momentarilyarrests the objects from forward movement until the lifting jet becomeseffective to elevate the objects over the barrier whereupon the objectsare again accelerated but at a reduced velocity. The forward momentum ofslow-moving objects, however, is not sufficient to permit the object tofully penetrate through the large airjet before the jet becomeseffective to lift the object to a height sufiicient to clear thebarrier. The rate of forward movement of the slow-moving objects is thusnot significantly affected or retarded by the interposition of thevelocity control device. The velocity control device in each instancediscriminates between fast and slow-moving objects on the air conveyorand thus does not affect accumulation recovery rates.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States LettersPatent is:

l. A conveyor for moving objects in a generally horizontal direction byutilizing airjets comprising; an elongated, substantially horizontallydisposed, conveyor deck having a plurality of openings therethrough fortransmitting air from the lower to the upper side thereof, said openingsbeing arranged such that the aiijets issuing therethrough are adapted toconvey objects along a predetermined path contiguous to and spaced abovesaid deck, means for arresting the movement of the objects along saidpath including a barrier disposed in the path of movement of theobjects, and means for enabling the objects to move past said arrestingmeans to continue their movement along said predetermined path includingmeans arranged to direct air against the objects to elevate the latterto a height above said barrier. I

2. A conveyor according to claim 1 wherein said openings comprise liftholes and directional slots configured such that the airjets issuingtherethrough have respective predominantly vertical flow components forelevating objects above said deck and predominantly horizontal flowcomponents for propelling the objects along said predetermined path.

3. A conveyor according to claim 2 wherein said directing means includesan opening in said deck adjacent said arresting means, the vertical flowcomponent of the airjet issuing through said latter opening beinggreater than the vertical flow component of the airjets issuing throughthe lift holes at locations along said deck other than the locationtherealong of said arresting means.

4. A conveyor according to claim 1 including means for adjusting theheight of said barrier above said deck.

5. A conveyoraccording to claim 1 wherein said barrier comprises anelement movable longitudinally between first and second positions, meansfor biasing said element into said first position including a spring,said element being movable from said first position to said secondposition against the bias of said spring when the objects engage saidelement.

6. A conveyor according to claim 5 wherein element is a rod extendingacross said deck, means for mounting said rod including brackets onopposite sides of said deck, said brackets having slots inclinedupwardly and forwardly in the direction of conveyance, the opposite endsof said rod being receivedv within said slots, said spring being adaptedto bias said rod into a lowermost position in said slots whereby saidrod is movable upwardly and forwardly against the bias of said spring inresponse to the engagement of the objects against said rod.

7. A conveyor according to claim 1 wherein said barrier comprises aplate having at least a portion thereof elevated above said deck and inthe path of movement of the objects, said plate having a plurality ofopenings therethrough for transmitting air from the lower to the upperside thereof, said openings being arranged such that the airjets issuingtherethrough are adapted to convey objects therealong and in spacedrelation thereto.

8. A conveyor according to claim 7 wherein said plate is pivotallycarried by said conveyor, the elevated portion of said plate comprisingan edge of said plate, the area between said plate edge and saidconveyor deck forming a slot for directing air against the objects andelevating the latter to a height above said plate edge.

9. A conveyor according to claim 8 including means for adjusting theheight of said plate edge above said conveyor deck. 10. A conveyoraccording to claim 1 wherein said barrier includes an element extendingacross said deck, guide means mounting said element for free verticalmovement, stop means mined path of movement of the objects, saiddirecting means being arranged todirect air against said element to liftsaid element and maintain it in a fixed floating position bearingagainst said stop means.

11. A conveyor according to claim 10 including means for adjusting theheight of said stop means above said deck.

12. A conveyor according to claim 10 wherein said directing meansincludes an opening in said deck underlying said element, and a bafflefor directing air against the underside of the objects as they obtainpositions adjacent said element on the upstream side thereof.

13. An air conveyor for moving objects in a generally horizontaldirection by aiijets comprising: an elongated, substantiallyhorizontally disposed, conveyor deck having a plurality of openingstherethrough for transmitting air from the lower to the upper sidethereof, said openings being arranged such that the air issuingtherethrough is adapted to convey an object along a predetermined pathcontiguous to and spaced above said deck, means disposed at apredetermined location along the conveyor for arresting the movement ofthe object along said path, means for enabling the object to move pastsaid arresting means and to continue its movement along saidpredetermined path including an airjet adapted to direct air against theobject to displace it from said predetermined path and thereby avoidsaid arresting means.

14. An air conveyor according to claim 13 including means coextensivewith and underlying said deck defining a fan, said deck forming an upperwall portion of said plenum, and a blower disposed at one end of saidplenum for supplying air under pressure to said plenum for flow throughthe openings in said deck.

i i i 1

1. A conveyor for moving objects in a generally horizontal direction byutilizing airjets comprising; an elongated, substantially horizontallydisposed, conveyor deck having a plurality of openings therethrough fortransmitting air from the lower to the upper side thereof, said openingsbeing arranged such that the airjets issuing therethrough are adapted toconvey objects along a predetermined path contiguous to and spaced abovesaid deck, means for arresting the movement of the objects along saidpath including a barrier disposed in the path of movement of theobjects, and means for enabling the objects to move past said arrestingmeans to continue their movement along said predetermined path includingmeans arranged to direct air against the objects to elevate the latterto a height above said barrier.
 2. A conveyor according to claim 1wherein said openings comprise lift holes and directional slotsconfigured such that the airjets issuing therethrough have respectivepredominantly vertical flow components for elevating objects above saiddeck and predominantly horizontal flow components for propelling theobjects along said predetermined path.
 3. A conveyor according to claim2 wherein said directing means includes an opening in said deck adjacentsaid arresting means, the vertical flow component of the airjet issuingthrough said latter opening being greater than the vertical flowcomponent of the airjets issuing through the lift holes at locationsalong said deck other than the location therealong of said arrestingmeans.
 4. A conveyor according to claim 1 including means for adjustingthe height of said barrier above said deck.
 5. A conveyor according toclaim 1 wherein said barrier comprises an element movable longitudinallybetween first and second positions, means for biasing said element intosaid first position including a spring, said element being movable fromsaid first position to said second position against the bias of saidspring when the objects engage said element.
 6. A conveyor according toclaim 5 wherein element is a rod extending across said deck, means formounting said rod including brackets on opposite sides of said deck,said brackets having slots inclined upwardly and forwardly in thedirection of conveyance, the opposite ends of said rod being receivedwithin said slots, said spring being adapted to bias said rod into alowermost position in said slots whereby said rod is movable upwardlyand forwardly against the bias of said spring in response to theengagement of the objects against said rod.
 7. A conveyor according toclaim 1 wherein said barrier comprises a plate having at least a portionthereof elevated above said deck and in the path of movement of theobjects, said plate having a plurality of openings therethrough fortransmitting air from the lower to the upper side thereof, said openingsbeing arranged such that the airjets issuing therethrough are adapted toconvey objects therealong and in spaced relation thereto.
 8. A conveyoraccording to claim 7 wherein said plate is pivotally carried by saidconveyor, the elevated portion of said plate comprising an edge of saidplate, the area between said plate edge and said conveyor deck forming aslot for directing air against the objects and elevating the latter to aheight above said plate edge.
 9. A conveyor according to claim 8including means for adjusting the height of said plate edge above saidconveyor deck.
 10. A conveyor according to claim 1 wherein said barrierincludes an element extending across said deck, guide means mountingsaid element for free vertical movement, stop meaNs above said deck forlimiting the elevation of said element above said deck and locating saidelement in the predetermined path of movement of the objects, saiddirecting means being arranged to direct air against said element tolift said element and maintain it in a fixed floating position bearingagainst said stop means.
 11. A conveyor according to claim 10 includingmeans for adjusting the height of said stop means above said deck.
 12. Aconveyor according to claim 10 wherein said directing means includes anopening in said deck underlying said element, and a baffle for directingair against the underside of the objects as they obtain positionsadjacent said element on the upstream side thereof.
 13. An air conveyorfor moving objects in a generally horizontal direction by airjetscomprising: an elongated, substantially horizontally disposed, conveyordeck having a plurality of openings therethrough for transmitting airfrom the lower to the upper side thereof, said openings being arrangedsuch that the air issuing therethrough is adapted to convey an objectalong a predetermined path contiguous to and spaced above said deck,means disposed at a predetermined location along the conveyor forarresting the movement of the object along said path, means for enablingthe object to move past said arresting means and to continue itsmovement along said predetermined path including an airjet adapted todirect air against the object to displace it from said predeterminedpath and thereby avoid said arresting means.
 14. An air conveyoraccording to claim 13 including means coextensive with and underlyingsaid deck defining a fan, said deck forming an upper wall portion ofsaid plenum, and a blower disposed at one end of said plenum forsupplying air under pressure to said plenum for flow through theopenings in said deck.